Ultra high frequency transmitter



Dec. 13, 1949 0, Km r AL 2,490,968

ULTRA HIGH FREQUENCY TRANSMITTER 2 Sheets-Sheet 1 Filed July 30, 1946 o m 1 m VWW/ZII Z/A IIAZ Dec. 13, 1949 E. O. KEIZER ET AL ULTRA HIGH FREQUENCY TRANSMITTER 2 Sheets-Sheet 2 Filed July 30, 1946 Gttomeg T 0 w ,MM m N zm e v E 6! u .5. v 52 wwm mg Patented Dec. 13, 1949 ULTRA HIGH FREQUENCY TRANSMITTER Eugene o. Keizer, Hal-wick Johnson, Vernon n.

Landon, and Robert L. Harvey, Princeton, N. J assignors to Radio Corporation of America, a

corporation of Delaware Application July 30, 1946, Serial No. 687,196

16 Claims.

, 1 This invention relates to ultra high-frequency equipment and particularly to oscillators which may be frequency modulated by variation of the anode circuit capacity of the oscillator tube.

In accordance with one aspect of the invention, and specifically as applied to a grounded grid oscillator utilizing a "lighthouse tube or equivalent, the grid terminal of the tube is connected to tubular structure forming the outer conductors of two oppositely extending concentric lines which enclose the tube and whose inner'conductors are respectively connected to the cathode and. anode terminals of the tube thus to form tuned input and output circuits therefor. More specifically, the cathode-grid line is resonant at one or other odd number of quarter wave lengths, and the anode-grid line is resonant at one or other integral number of half wave lengths, which relation facilitates frequency modulation of the oscillator output by variation of the capacitance of one of said lines, as by vibration, at modulation frequencies, of a capacitor element.

In accordance with a more general aspect of the invention, the oscillator tube and one of the concentric lines are removable as a unit from the other line and associated parts, thus to facilitate tube replacement; more particularly, the line of joinder of the separable units is so selected that the joint is in a region of low current density so to avoid leakage of high-frequency energy. Preferably and more specifically, the anode-grid line is comprised in an intermediate unit, to one end of which is disengageably attached the aforesaid tube and cathode line unit and to the other end of which is disengageably attached a modulator unit for varying the capacity of the anode-grid line. I

The invention further resides in features of construction, combination, and arrangement hereinafter described and claimed.

For more detailed understanding of the invention and for illustration of several modifications thereof, reference is made to the accompanying drawings'in which:

Figure 1 is a front elevational view, in section, of an oscillator stage;

Figure 2 is a plan view with parts broken away, and partly in section, of Figure 1;

Figure 3, on enlarged scale and in section, shows a feedback link arrangement used in Figures 1 and 2;

Figure 4 is a fractional view, in section, showing a modification of the feed-back arrangement of Figure 3;

Figure 5. in section, shows a tunable concentric 2 line which may be used in substitution for feed-' back arrangements disclosed in Figures 3 and 4;

and

Figure 6 is a front elevational view of an oscillator stage in general similar to but specifically diflerent from that shown in Figure 1.

Referring to Figure 1, the tube I0 is of the lighthouse type, such as the 2043 or similar tube, having its anode, grid and cathode terminals spaced longitudinally of the tube in the order named. The cathode terminal 13 of the tube is engaged by the spring fingers of an annular terminal l4 attached at or near its outer periphery to the metal ring l5 suitably secured to the upper end of the inner conductor l6 of a concentric line i! which is, or is adjustable to be, one or other odd number of quarter wave lengths long at the desired operating frequency. The effective length and therefore the resonant frequency of the line I! is variable by adjustment of the shorting ring l9 provided with two sets of spring fingers 20 and 2| respectively engaging the exterior surface of the inner conductor l6 and the interior surface of the outer conductor l8 of the line. Ring is is attached to the annular plunger I00 which slidably engages the inner and outer walls respectively of conductors l8 and IS.

The lower end of the line H is closed by the end ring 22 suitably attached as by soldering to the inner and outer conductors l6 and Hi. The central opening of the ring 22 is of diameter sufficientlylarge to permit passage therethrough of the tube [0 into the housing afforded by the inner conductor I6 of line II. This chamber or space is closed by the end plate 24 suitably removably held as by screws 23 which pass through plate 24 threadedly to engage the ring 22. The lower face of the socket 25, which receives the pins, not shown, extending from the base of tube III for connection thereto of the source of heater current and the direct-current cathode connection, rests upon the upper end of a hollow'plunger 26 within which is disposed a biasing spring whose lower end bears against the threaded plug 28 in the end plate 24. The lower end of the plunger 26 is received by the guide ring 29 attached to the inner face of plate. 24 and having slots which receive the pins 30 extending laterally from the plunger 26, the ends of the slots by their cooperation with pins 30 limiting the extent of movement of the plunger. As hereinafter appears, the plunger 26 forces the tube In upwardly to limiting position determined by engagement between the anode terminal of the tube and its associated fixed contact. The conductors 3|, for supplying the spring fingers of an annular contact ring 32 suitably attached adjacent its periphery to the cap member 33 which forms a continuation of the outer conductor l8 of line H and, as hereinafter appears, also as a continuation of the outer conductor of the anode-grid line to which it is attached as by soldering. The unit comprising the cathode-grid line I! and tube I is held against the member 33 by the clamping ring 34 which threadedly engages the outer periphery of ring 33 and which is provided with a lower inturned edged or lip which hooks under the shoulder provided by the peripheral rib 35 extending around outer conductor [8 near its upper edge. As more clearly show in Figure 3, the underface of cap 33 is recessed to receive the upper end of the conductor l8 so that the joint between conductor l8 and cap 33 is a dual one, there being two offset areas 36 and 31 at which pressure is applied when the clamping ring 34 is tightened. It should be noted that this joint between the members I8 and 33 is at a region of low current density in the resonant grid-cathode circuit and that consequently the escape of radio-frequency energy through the joint is minimized. Furthermore, the clamping ring 34, also of metal, overlies the joint and thus provides another seal area at 38 which further increases the length of any possible path of escape of high-frequency energy. By unscrewing the clamping ring, the lower unit comprising tube l0 and the cathodegrid line can be withdrawn simply by pulling it away from the remainder of the oscillator assembly.

The tubular member 39 forms the main part of the outer conductor of the anode-grid line 40 whose inner conductor is comprised in part by the annular terminal member 4| which receives the anode cap or terminal ll of tube I0, and in part by the conductor 42 extending upwardly from member 4| axially of tube member 39. Member 4| also serves as a stop against which tube I0 is forced by the spring 21. For reasons which hereinafter appear, the conductor member 42 is threaded to provide for its axial adjustment. The flanged member 43 extending outwardly and upwardly from the upper end of the outer conductor 39 is suited removably to receive a modulator unit 44 comprising a casing 45 held in position against and within member 43 by clamping ring". The diaphragm 41 of the modulator unit has attached thereto a tubular capacitor element 48 concentric to the inner conductor member 42 of the anode line. Vibration of the diaphragm 41, and therefore variation of the capacity between the members 42 and 48, is effected by the voice coil 49 energized from any suitable source of modulating current. The voice coil is supported upon a form attached to the diaphragm 41 and is movable in the annular gap between the pole pieces 58 and 5| of a magnet structure heldin suitable position within the casing 45, as by the screws 52.

The mean frequency at which the anode-grid line 40 is resonant may be varied by adjustment of the rod 53 having at its lower end a capacitor plate 54 and whose upper end is accessible for adjustment exteriorly of casing 45 by removal of the cap 55. For a given amplitude of vibration of diaphragm 41, the percentage frequency modulation is predetermined by the setting or adjustment of member 42. This modulator unit is generally of the type disclosed and claimed in copending application, Serial No. 601,798, Johnson et al., now Patent No. 2,482,914, issued September 27, 1949. Depending upon the source of modulating current, the resonant frequency of the anodemodulation by capacity variation of the line because the capacity variation may thereby be introduced at an electrically high impedance point on the line, allowing a wide range of frequency variation for a small change in capacity.

To provide for supply of direct current to the anode and yet prevent escape of radio-frequency energy from the anode line, there is provided a stub line 56 comprising an outer conductor 51 terminating at its junction with the outer conductor 39 of the anode line and an inner conductor 58 which terminates at and supports the anode terminal 4|. The stub line 56 is a closed line and in electrical length is one-quarter wavelength or other odd number of quarter wavelengths long, so that its input end is seen by the line 40 is a very high impendance. The outer end of the inner conductor 58 is connected to and supported by a plate 59 which serves as one plate of a by-pass condenser whose other plate is formed by the Op ing surface of the casing 50 to which plate 59 is held by screws 6| insulated therefrom. The outer end or termination of stub line 56 therefore appears, because of the length of the line and the by-pass condenser, as a low impedance to the high-frequency component of the anode current. The dielectric of the condenser is provided by a thin sheet 62 of mica, or equivalent. The plate supply lead 64 may be secured and electrically connected to the inner conductor 58 by the nut 53 which secures that conductor to the plate 59. As shown in Figs. 1 and 2, the inner conductor 58 from the anode is massive to resist deflection by spring 21 and is in intimate thermal relation to the anode for conduction of heat therefrom.

The concentric line 65 for feeding the output of the oscillator to an antenna, to the attenuator of a signal generator, or to any other load, comprises an outer conductor 86 threadably received by the outer conductor 39 of line 48 or by a .boss extending therefrom, and it is locked in position affording the desired load coupling by the nut 61. The inner conductor 58 of the line 65 may extend into thespace between the inner and outer conductors of line 4|! as a capacity probe or, as shown,-may terminate ina loop 59 whose other end is connected to the outer conductor 66. The output end of inner conductor 68 is provided with a socket-fitting 18 to receive, for example, the inner conductor of a concentric feed-line.

The feed-back coupling between the cathode and anode lines may be afforded, Figures 2 and 3, by an untuned, non-adjustable feed-back link terminating in loops l2 and I3 disposed respec.

tively in the space between the inner and outer conductors of the anode line and of the cathode line. As shown, the connection between corresponding ends of the two loops is formed by a conductor I4 disposed within the tubular outer conductor or shield which passes through the cap member 33 and is suitably attached thereto or to the inner face of the outer conductor 39. The loop-coupling has a wide-band characteristic insuring continued generation of oscillations throughout the range of frequencies over which the resonant frequency of the anode line is swept by vibration of diaphragm 41 of the modulator unit. 1

In some such systems, such as, for example, that disclosed in Fig. 4 of copending application, Serial Number 693.506, filed August 28. 1946, the oscillator is utilized both as the oscillator of a transmitter and an oscillator in a receiving system. For that purpose, there is provided a second output line I8, Figure 2, for connection to the mixer stage of a receiver. Line 16 comprises an outer conductor 'I'I connected to the outer conductor 39 of the anode line 40 and an inner conductor 18 whose input extension 19 provides for capacitive or inductive coupling between the lines 40 and 16. The input end of the line 16 is re-- ceived by the terminal fitting 80 whose stationary part 8|, suitably attached to the outer conductor of line 40, receives the clamping nut 82.

In the modification shown in Figure 4, the loo providing for inductive coupling with the cathode line is formed by connection of the output con- The construction shown in Figure 6 is similar to that illustrated in Figure 1, inthat there are the same general physical and electrical relations between the tube and the concentric lines asso- .ciated therewith and therefore. a The corresponding parts have been identified by the same reference characters as in Figure l with the addition of the suffix A. In Figure 6 there are shown the rods IOIA for adjusting the shorting ring ISA in the cathode line. may be used for tuning the corresponding line in Figure 1, or the ring H9 or ISA) may be preadjusted for operation at a fixed frequency or for narrow range of frequencies. It shall be understood that in many of the features the constructions shown are not limited to an oscillator stage but may be used, for example, in amplifier, demodulator, and mixer stagesvutilizing tubes of the general type shown l. A frequency-modulated oscillator comprising an electronic tube having anode, grid and number of quarter wave lengths, concentric conductor 83 to one of the spring fingers MB of the annular cathode terminal M. The loop so formed may be comprised in a feed-back link or for any other purpose. It may, for example, connectto the inner conductor of a tunable link circuit such as shown in Figure 5 and now described.

The trombone or tunable concentric'line 84 is comprised of three sections: 85, 86 and 81. The

section 85 comprises an outer conductor 88 85 is maintained by the spacers 9| of suitable in- I sulating material.

The inner diameter of the outer conductor 92 of line section 81 is suited snugly and slidably to receive the line section 85, the end of conductor 92 being slotted as shown to provide spring fingers 92A which insure good electrical contact between the line sections. The proper spacing between the inner and-outer conductors 92 and 93 of the slidable line section 81 is maintained by the discs or blocks 94 of suitable insulating material. 7 i

The outer conductor 95 of the other stationary line section 86 is threaded for reception, for example, by the threaded opening 99, Figure 4, in the outer conductor i8 of the cathode line of the oscillator. The inner conductor 96 of line section 86 is hollow, slidably to receive at one end the inner conductor 93 of the adjustable section 81 of the trombone, and at its other end to receive pickup element 9'! which may be a capacity probe or loop, or a conductor for connection to'such an element; for example, to the conductor 83 of Figure 4.

. tively disposed in said sections to provide feedductors respectively connected to said grid and anode terminals and forming a concentric line resonant at an integral number of half wave lengths, and modulating means for varying the capacity of said grid-anode lineat a high-impedance region-thereof.

2. A frequency-modulated oscillator comprising an electronic tube having anode, grid and cathode terminals spacedin ordernamed longitudinally of the tube, tubular conductor structure surrounding said tube, conductors respectively connected to said anode and grid terminals and extending therefrom in opposite directions within said tubular conductor structure to comprise therewith resonant concentric line sections, an annular conductor connecting said tubular conductor structure to said grid terminal and closing the adjacent ends of said sections externally of the tube, modulating means for varying the resonant frequency of one of said line sections over a range of frequencies, and a link circuit comprising loops respectively disposed in said sections to provide feed-back coupling therebetween for continuous generation of oscillations throughoutsaid range of frequencies.

3. A requency-modulated oscillator comprising an electronic tube having anode, grid and cathode terminals spaced in'order named longitudinally of the tube. tubular conductor structure surrounding said tube, conductors respectively connected to said anode and grid terminals and extending therefrom in opposite direction within said tubular conductor structure to comprise therewith resonant concentric line sections, an annular conductor connectingsaid tubular conductor structure to said grid terminal and closing the adjacent ends of said sections externally of the tube, modulating means for varying the resonant frequency of one of said line sections over a range of frequencies, and a link circuit wholly within said tubular conductor comprising loops respecback coupling therebetween for continuous generation of oscillations throughout said range of frequencies.

4. An oscillator comprising an electronic tube A similar arrangement having anode, grid and cathode terminals spaced opposite directions within said tubular conductor structure to comprise therewith resonant concentric line sections, an annular conductor connecting said tubular conductor structure to said grid terminal and closing the adjacent ends of said sections externally of the tube, and a link circuit comprising loops respectively disposed in said sections and forming terminations of a concentric line external to said tubular conductor structure.

5. An oscillator comprising an electronic tube having anode, grid and cathode terminals spaced in order named longitudinally of the tube, tubular conductor structure surrounding said tube, conductors respectively connected to saidanode and grid terminals and extending therefrom in opposite directions within said tubular conductor structure to comprise therewith resonant concentric line sections, an annular conductor connecting said tubular conductorstructure to said grid terminal and closing the adjacent ends of said sections externally of the tube, and a tunable link circuit comprising loops respectively disposed in said sections and forming terminations of a concentric line external to said tubular conductor structure and extensible for tuning.

6. A grounded-grid frequency-modulated oscillator whose grid-anode and grid-cathode circuits comprise closed-ended concentric lines having a common outer conductor enclosing the oscillator 'tube, the grid-cathode line being resonant at an odd number of quarter wave lengths and the gridanode line at an integral number of half wave lengths, and means for vibrating the closed-end of the grid-anode line at modulation frequencies.

7. A grounded-grid frequency-modulated feedback oscillator whose grid-a'node and grid-cathode circuits comprise concentric lines having an outer conductor enclosing the oscillator tube, the grid-cathode line being resonant at an odd number of quarter wave lengths and the grid-anode line at an integral number of half wave lengths, modulating means for varying the capacity of said grid-anode line at a region of high impedance to vary the resonant frequency of said line over a range of frequencies, and the feed-back coupling between said circuits being effected by a link cir-- cuit terminating ,in loops disposed respectively within said lines for continuous generation of oscillations throughout said range of frequencies.

8. An oscillator comprising an electronic tube having anode, grid and cathode terminals spaced longitudinally of the tube, concentric conductors respectively connected to said grid and cathode terminals and forming a concentric line resonant at an odd number of quarter wave lengths, concentric conductors respectively connected to said grid and anode terminals and forming a concentric line resonant at an integral number of half wave lengths, a variable capacitor within and connected to the conductors of the last-named line, and means for varying the capacity of said variable capacitor at modulation frequencies.

' 9. An oscillator comprising an electronic tube having anode, grid and cathode terminals, concentric conductors respectively connected to said grid and cathode terminals and forming a concentric line resonant at an odd number of quar- 8 nals, the ratio of the inner diameter of the outer conductor to the outer diameter of the inner conductor being with the range of from about 3.5:1 to about 4:1 and said conductors forming a concentric line resonant at an integral number of half wave lengths.

10. A frequency-modulated oscillator comprising an electronic tube having external anode, grid and cathode terminals spaced longitudinally of the tube in the order named, structure connected to said grid terminal and defining a cavity about said anode terminal, conductive members spaced at a high-impedance region within said cavity and respectively connected to said anode terminal and to said member, means for varying the spacing between said members capacitatively to vary the frequency for which said cavity'is resonant, tubular conductors respectively connected to said grid and cathode terminals and forming a second resonant cavity, and a feed-back link circuit terminated in loops respectively disposed in said cavities for continued generation of oscillations I over the range of frequency variation of said first-named cavity.

11. A frequency-modulated oscillator comprising an intermediate unit including a concentric line, a modulator unit disengageably'connected to one end of said line and including a vibratory member for varying the resonant frequency of an oscillator circuit formed by said line, a third unit disengageably connected to the other end of said line and comprising a second concentric line and an electronic tube, annular terminals attached to conductors of said lines for connection respectively with the anode, grid and cathode terminals of said tube, and a feed-back link physically attached to one of said lines and providing coupling between them when said third unit is connected to said intermediate unit.

12. A frequency-modulated oscillator comprising an intermediate unit including a concentric line, a modulator unit disengageably connected to one end of said line and including a vibratory member for varying the resonant frequency of an oscillator circuit formed by said line, a third unit disengageably connected to the other end of said line and comprising a second concentric lineand an electronic tube, annular terminals attached to conductors of said lines for connection with the anode, grid and cathode terminals of said tube, a feed-back link physically attached to one of said lines and providing coupling between them when said third unit is connected to said intermediate unit, a stub line extending from said intermediate unit for feedthrough of direct current to the annular terminal engaging the anode terminal of the tube. and heater circuit connections extending through the inner conductor of said second concentric line to heater terminals of said tube.

13. A frequency-modulated oscillator comprising an intermediate unit including a concentric line, a modulator unit disengageably connected to one end of said line and including a vibratory member for varying the resonant frequency of an oscillator circuit formed by said line, a third unit disengageabfy connected to the other end of said line and comprising a second concentric line and an electronic tube, annular terminals attached to conductors of said lines for connection with the anode, grid and'cathode terminals of said tube, and an output pick-up element coupled to the circuit formed by one of said lines and pfhysically attached to the outer conductor there- 0 9 14. A high-frequency stage comprising two aligned concentric lines, annular terminals connected to the inner conductors of said lines for engagement with the anode and cathode terminals of a tube housed by said lines, an annular terminal attached to the outer conductor of one of said lines for engagement with the grid terminal of said tube, said last-named annular terminal and the outer conductor of the other of said lines having complementarily shaped faces forming a multi-face joint minimizing leakage of high-frequency energy, and a clamping ring for disengageably connecting the outer conductors of said lines and overlapping said joint, said tube and said other of said lines being linearly retractable as a unit upon release of said clamping ring.

15. Structure suited in combination with an electronic tube having longitudinally spaced anode, grid and cathode terminals to form a highfrequency frequency-modulated oscillator and comprising two concentric lines having a common outer conductor for connection to said grid terminal and whose inner conductors are respectively for connection to said anode and cathode terminals, the grid-cathode line being resonant at an odd number of quarter wavelengths and the anode-grid line being resonant at an interval number of half wave lengths and modulating means for varying the capacity of said grid-anode line at a region of high impedance.

16. A high-frequency device for housing and forming circuit elements associated with an electronic tube of the type having concentric electrode terminals spaced longitudinally of the tube comprising two concentric lines whose electrical lengths are respectively an odd number of quartier-wavelengths and an integral number of halfwavelengths, the inner conductors of said lines meeting at their connection to the anode of said tube and the outer conductors of said lines meeting adjacent the anode for connection to another electrode of said tube, the first of said lines providing for supply of direct current to said anode and having a termination of low-impedance to the high-frequency component of the anode current, and the other of said lines having a capacitive termination of high-impedance to said highfrequency component.

EUGENE O. KEIZER. HARWICK JOHNSON. VERNON D. LANDON. ROBERT L. HARVEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 

